Apparatus for forming hollow articles



Sept. 16, 1969 c. l.. wHlTl-:FORD

APPARATUS FOR FORMING HOLLOW ARTICLES 15 Sheets-Sheet l Filed Feb. 13,1967 F/ Gf 5 lllll E UR U mm B o A m FR MP m UW MA mf Ww F WN EO m RM RTP PA W. T MG N M E O N El LU HR E0 P R Pm u B m R S NWS NNA M Ul NR Ewom mme .H E O S M CR FSF EP MHC J Nw PFW o EG M m .Nl A LGR www WFH N OC D RF mm m H VW W L w R A C Sept 16,` 1969 c. l.. wHn'EFoRD 3,466,908

APPARATUS FOR FORMING HOLLOW ARTICLES Filed Feb. 13, 1967 l5Sheets-Sheet 2 92 m /02 v T V o--o a/ fw CARLTON L. WHITEFORD Sept. 16,l

Filed Feb. 13, 1967 C. L. WHITEFORD APPARATUS FOR FORMING HOLLOWARTICLES 15 Sheets-Sheet 3 AT TORNEY Sept. 16, 1969 C. 1 wHrrEFoRDAPPARATUS FOR FORMING HOLLOW ARTICLES l5 Sheets-Sheet 4 Filed Feb. 13,196'? TTURNEY sept. 16, 1969 c. n.. wHn'EFoRD 3,466,908

APPARATUS FOR FORMING HOLLOW ARTICLES Filed Feb. 13, 1967 l5Sheets-Sheet 5 INVENTOR. CARLTON L. WHITEFORD A TTORNE' Y Sept. 16, 1969c. L. wHlTr-:FQRD 3,455,908

APPARATUS FOR FORMING HOLLOW ARTICLES Filed Feb. 1s, 19e? 15 sheetssheete g ,H 62 'il mii! 4d 11 'll ll il Yil 42k/ lr 70 lll INVENTOR.

CARLTON L. WHITEFORD ATTOR/VE) Sept. 16, 1969 c. L. WHITEFORD APPARATUSFOR FORMING HOLLOW ARTICLES 15 Sheets-Sheet '7 Filed Feb. 13, 196'? aniSept- 16, 1969 c. 1 .wHlTEr-ORD 3,466,908

APPARATUS FOR FORMING HOLLOW ARTICLES Filed Feb. 125, 1967 15Sheets-Sheet 8 INVENTOR.

CARLTON LA WHTEFORD A TTORNEY Sept. 16, 1969 c. L. WHITEFORD 3,466,908

APPARATUS FOR FORMING HOLLOW ARTICLES Filed Feb. 13, 1967 v 15Sheets-Sheet sa INVENTOR. CARLTON L.WHITEFORD BY V /fz /Z /fg ATTORNEYSept. 16, 1969 c. l.. wHrrEFoRD APPARATUS FOR FORMING HOLLOW ARTICLES 15Sheets-Sheet l O Filed Feb. 13, 1967 I\\ EINTOR.

CARLTON L, WHlTEFORD Q (/Mgf ATTRNEY sept. 16, 1969 Filed Feb. l5, 196'?C. L. WHITEFORD APPARATUS FOR FORMING HOLLOW ARTICLES Fmt/6 15Sheets-Sheet l1 F/G. /7 l; i W V I i HJIl ATTORNEY Sept 16, 1969 c. L.wHl'rl-:FORD

APPARATUS FOR FORMING HOLLOW ARTICLES l5 Sheets-Sheetl l 2 Filed Feb.13, 1967 F/GZO INVENTOR.

CARLTON L.. WHITEFORD Sept. 16, 1969 c. L. wHrrEFoRD APPARATUS FORFORMING HOLLOW ARTICLES Filed Feb. 1s, 1967 15 Sheets-Sheet 13 FIGJA'.Oll' o L1 in i 15 Sheets-Sheet 14 FI G. 27

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7 BY 7% Arm/wer Sept. 16, 1969 c. l.. wHn'EFoRD APPARATUS FOR FORMINGHOLLOW ARTICLES 15 Sheets-Sheet 15 Filed Feb. 13, 1967 /N VENT/f CA RLToN l, k/f//re rom:

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4 TTD/PA/EY United States Patent O 3,466,908 APPARATUS FOR FORMINGHOLLOW ARTICLES Carlton L. Whiteford, Stamford, Conn., assignor toPlastic Can Corporation, Springdale, Conn., a corporation of ConnecticutContinuation-impart of application Ser. No. 456,454, May 17, 1965, whichis a continuation-impart of application Ser. No. 313,071, Oct. 1, 1963.This application Feb. 13, 1967, Ser. No. 619,507

Int. Cl. B21d 22/20, 39/08 U.S. Cl. 72-58 16 Claims ABSTRACT F THEDISCLOSURE There is disclosed apparatus for fabricating hollow artcleswhich achieves substantial multiaxial orientation of ductile metal orsynthetic plastic by use of a combination including a pair of split moldmembers which are movable upon a frame into an operating positionwherein they define a mold cavity of desired wall configuration with theframe and split mold members providing cooperating portions for clampingthe periphery of a preform into operative position at one end of themold cavity. A pair of plunger means move together within the cavity endrelative to each other during movement inwardly of the mold cavity so asto draw the preform into an elongated side wall while at the same timeexpressing material from the clamped bottom of the preform for use informing the side Wall. Internal pressure applying means extend withinthe mold cavity during the inward movement of the plunger means to pressupon the internal surface of the preform and effect lateral expansionthereof into conformity with the wall of the mold cavity.

Various specic embodiments of the several components of the apparatusare disclosed. In addition, there is disclosed the structure of thepreforms utilized in the apparatus which have flanges extendingoutwardly adjacent the upper end of an incipient side wail portion so asto facilitate clamping thereof by the apparatus. Hollow metal containersare also disclosed and fabricated from preforms of ductile metal.

RELATED APPLICATIONS The present application is a continuation-in-partboth of my copending application Ser. No. 456,454, tiled May 17, 1965,now U.S. Patent 3,303,806, which in turn is a continuation in part of mycopending applications Ser. No. 313,071, led Oct. l, 1963, now U.S.Patent 3,184,524 g'ranted May is, 1965, and ser. No. 382,207, sied July13, 1964, now U.S. Patent 3,305,158, which in turn is a division of mycopending application Ser. No. 313,071, tiled Oct. l, 1963.

BACKGROUND OF THE INVENTION Heretofore, it has been well known thatgreat strength in relatively thin section can be obtained by use ofbiaxially oriented synthetic plastic material, thus making possibleeconomical, relatively high-strength containers of synthetic plasticmaterial. Generally, this has resulted in Widespread use of biaxiallyoriented sheet material for thermoforming into various conligurations.Such thermoforming occasionally may be disadvantageous in that the sheetmaterial may be drawn non-uniformly so that variable or very thin-wallsections may occur with resultant Weak points in the thermoformedstructure.

Moreover, in effecting a deep draw of the plastic sheet conventionallyused for thermoforming, the problem of non-uniform wall section isaggravated and thick sheeting must generally be used to providesufficient wall thickness in the drawn portion. Plug or other mechanicalas- ICC sist techniques are oftentimes employed to alleviate thesedifficulties in thermoforming, but generally blow-molding techniquesusing an elongate parison have been primarily employed for formingcontainers and other hollow articles having a relatively deep body orcavity. Generally, such blow-molded articles do not possess highmolecular orientation for optimum strength and utilization of materials.

Although the concepts of biaxially orienting synthetic plastic sheetmaterials are well known, the distinctions in the nature of metals andtheir processing characteristics have militated against the extension ofsuch concepts to metals. However, in the fabrication of metals it isknown that all but a few metals can be work-hardened or provided Withenhanced properties by producing ow of the metal at a temperature belowthat at which the metal will recrystallize. This practice is extensivelyemployed in the rolling, drawing, extrusion, and forging of metals aswell as in other techniques of effecting low temperature working. It isalso well known that certain metals are not susceptible towork-hardening, such as pure gold, and that other metals anneal atambient temperatures s0 that any hardening produced by the workingdisappears due to recrystallization at room temperature. Generally, theworking of metals has tended to produce a significant unbalancing ofproperties due to the fact that greater working will occur along thelongitudinal axis of the product than in the transverse direction.

It is an object of the present invention to provide a novel apparatusfor forming containers and other hollow articles of synthetic plasticmaterial or ductile metal wherein the plastic molecules or metalcrystals in the wall portions are substantially highly multiaxiallyoriented.

Another object is to provide such an apparatus for producingsubstantially multiaxially oriented articles wherein the wall thicknessof the articles may be closely controlled to achieve high strength andoptimum utilization of material for most economical practice.

It is also an object to provide containers and other hollow articleswith a body portion of highly multiaxially oriented metal and which arerelatively high strength and economical and which are controllable inwall thickness and variable in configuration.

A specific object is to provide a relatively high-strength 'andeconomical container for oils and other liquids which has a body portionsubstantially formed of highly multiaxially oriented metal and which isresistant to crushing pressures.

Yet another specic object is to provide a relatively high-strength andeconomical container for liquids under pressure such as carbonated andfermented beverages which has a body portion substantially formed ofhighly multiaxially oriented metal.

Still another object is to provide blanks of synthetic plastic materialand of ductile metal which are adapted to be readily and economicallyformed into articles wherein the molecules or crystals in the wallportions are highly multiaxially oriented and wherein the wall thicknessmay be eifectively predetermined.

SUMMARY OF THE INVENTION It has now been found that the foregoing andrelated objects can be readily attained by a method in which orientablesynthetic plastic material or relatively ductile metal is formed into apreform of predetermined configuration and then clamped about itsperiphery adjacent one end of a mold cavity of the desired wallconfigura- Ition. The center portion of the preform is then displacedinwardly of the mold cavity relative to the clamped periphery thereofwhile compressive pressure is simultaneously applied to both surfaces ofthe center portion to effect lateral flow of the material in the centerportion and provide material in the wall portion being formed betweenthe clamped periphery and the displacing center portion. After thecenter portion has been displaced fully inwardly of the mold cavity,pressure is applied to the interior of the displaced preform to expandor stretch it into conformity with the wall of the mold cavity to form ahollow article of the desired configuration. The displacement andpressure application are conducted below the molten temperatures of thesynthetic plastic material and at orientation temperatures thereof, orbelow the recrystallization temperature of the metal, to effectmolecular orientation during the inward displacement, lateral flow andexpansion of the preform material.

Various metals may be employed in the process of the present inventionwith varying effectiveness depending upon their ability to be formedrapidly at reasonable pres- `sures and their propensity towardscrystalline orientation and ability to retain such orientation atambient temperatures. For example, aluminum, magnesium, copper and brassmay all be drawn and extruded readily and so are particularly adapted tothe present invention. Similarly, various low carbon steels may bereadily formed and various other metals and alloys enjoy varying degreesof ductility.

A-s defined herein, the term relatively ductile metals includes thevarious metals and alloys in which fiow and deformation of the metal maybe effected at reasonable pressures and temperatures.

The term recrystallization temperature as used herein refers to thetemperature at which the oriented crystal structure produced by theprocess herein is rapidly transformed. Although some recrystallizationmay be tolerated, generally a significant amount should be avoided tomaximize the desirably attained properties.

The hollow articles produced by the present invention have substantiallyradial orientation of the plastic molecules or metal crystals in thebottom wall portion produced by the compressive deformation andstretching during final conformation. The side wall portion hassubstantially multiaxial orientation of the plastic molecules or metalcrystals due to the radial orientation produced in the materialcompressively expressed laterally for formation of the lower section ofthe side wall portion with substantial vertical or axial orientation dueto the axial displacement and stretching of the side wall portion andsubstantial transverse or peripheral orientation due to the stretchingduring final conformation. Thus, the plastic molecules or metal crystalsare substantially oriented along a plurality of axes, herein referred toas multiaxial orientation or multiaxially oriented.

The hollow articles of the present invention are desirable employed asdisposable containers because of their high strength and relatively lowcost. The closure for the opening of the container may be molded as apart of the preform, or a separate closure of metal, plastic or othermaterial may be employed. To enhance further the strength of the hollowarticle, it may be provided with a peripheral reinforcing band ofmaterial, desirably uniaxially oriented synthetic plastic which has beenoriented in the peripheral direction or metal foil.

Since it is quite important that the material of the preform bestretched uniformly and also that the method be conducted as rapidly aspossible for optimum economy, the preform preferably is soaked to auniform temperature throughout its thickness prior to introduction intothe mold cavity, conveniently by hot air, oil or other suitable meansfor a sufficient period of time. Conveniently, this soaking may becarried out continuously on a conveyor or in a group or batch in aseparate section of the apparatus, thus permitting preheating of thepreforms before insertion into the mold cavity. To minimize any tendencyfor the clamped periphery to be stretched and thus disengaged under theconsiderable pressures employed, the clampingV elements (or moldcomponents) preferably are unheated or chilled so as to extract heattherefrom. However, particularly with some of the highly ductile metals,the process may be carried out with the preform at ambient temperaturedepending upon the power capacity of the press and the depth of thesidewall portion to be formed.

The temperatures employed in the process should be below the moltentemperature of the plastic or recrystallization temperature of the metalsufficiently so that there is no likelihood that incipient melting orrecrystallization will occur during the pressure forming as a result ofthe energy introduced into the material by reason of the extensive workbeing performed therein at substantial pressures. However, highorientation temperatures commensurate with the safety factor aredesirable to reduce the pressures required for pressure deformationparticularly with the less ductile alloys of iron. For example,polypropylene has a melting temperature of about 330 Fahrenheit and isgenerally preheated to about 200 to 300 Fahrenheit, and preferably 250to 290 Fahrenheit.

The displacement of the center portion of the preform and thecompression thereof is effected by a pair of cooperating plunger or diemeans on opposite surfaces of the center portion which both moverelatively inwardly of the mold cavity to effect the desireddisplacement and one or both ofV which move towards the other during thedisplacing movement to effect the compressive pressure upon the preformmaterial. The movement of the two pluagers relative to each other shouldbe closely controlled to obtain the desired rate of lateral flow orexpression of the preform material from between the plungers to form arelativey uniform thickness in the wall portion being formed as thecenter portion of the preform is being displaced inwardly. Thissynchronization and control of movement may be effected by gears, cams,hydraulic control means, electrical circuitry, combinations thereof orother suitable control means, as will be apparent hereinafter.

The pressures employed will vary upon the temperature of the plasticmaterial or metal at the time of deformation and compression, itsresistance to deformation and the time period employed. For example, informingV a polypropylene preform which has been preheated to about 280Fahrenheit, 5 to 20 tons pressure is satisfactorily employed to effectthe inward displacement and 25 to 65 tons is satisfactorily employed toeffect the compression and flow to elongate the preform about ten timesin a period of about three seconds.

The pressures employed for a given metal generally coincide with thoserequired for extrusion of the metal. By use of apparatus such asdisclosed herein, the speed of compression of the center portion of thepreform and/or the pressure employed therefor, as well as the shape ofthe preform, may be readily adjusted to provide the desired expressionradially of only that material required at a given moment for thesidewall portion being formed. In this manner, the factors required fora given article and metal preform may be readily determined byobservation of flow lines within the metal and the thickness of themetal in the sidewall portion.

To avoid premature chilling of the preform, at least the contactingfaces of the plungers should be heated to the desired temperature fororientation conveniently by impulse heating elements on the facethereof, although conventional heating elements may be employed in thebody thereof albeit with greater difficulty in effecting the desiredchilling and setting of the material upon completion of the formingcycle.

The plunger on the inside surface of the preform is of lesser width thanthe mold cavity so that the wall portion of the preform being formedduring the inward displacement tapers inwardly from lthe clampedperiphery and thus is spaced from the wall of the mold cavity. In thismanner, friction is minimized and premature chilling and setting of thematerial by contact with the mold wall is eliminated since the mold wallis desirably cooled to effect the desired chilling and setting uponfinal conformation of the material.

The cooperating faces of the plungers and the wall of the mold cavitymay be smooth or they may have various configurations to provide desiredcharacteristics or appearance in the final article. For example, axialcorrugations or ribs may be provided in the mold to provide verticalcorrugations in the article for greater vertical strength in the finalarticle, or peripheral corrugations or ribs may be provided in the moldwall to provide peripheral corrugations in the article for greaterperipheral strength. The plunger die faces may be cooperativelyconfigured to provide `a ribbed concave bottom wall for4 a pressurecontainer, or the outer plunger and mold wall may have cooperatingperipheral recesses to provide a skirt or bead at the juncture of theside and bottom Walls of the finished article.

The final deformation of the preform after the center portion has beenfully displaced inwardly is effected by means which Will effectsubstantially uniform pressure throughout the interior surface of thepreform. Air or other fluid at relatively high pressures may be directlyintroduced into the preform to effect the final stretching andconformation, but concentrated impingement at any one point should beavoided. Oil or other uid may be admitted to an expandible bladder orpolyurethane or other heat-resistant and high-strength materialmaintained in a recess behind the plunger face to expand the bladder andpress the preform into conformity with the mold cavity wall. As anotheralternative, a mass of resiliently deformable material which is heatresistant and relatively noncompressible may be maintained in a recessbehind the plunger face and deformed by mechanical action to press thepreform material against the mold wall.

The preform has a configuration and dimensions predetermined to producethe desired wall thicknesses in the final article and permit the desiredpressure deformation to obtain crystalline or molecular orientation.Generally, the preform desirably is dish-shaped with an outwardlyextending peripheral ange for clamping in the mold and the sidewallportion preferably is inclined inwardly to facilitate the formation ofinwardly tapering or inclined sidewall portion during displacement ofthe preform and the spacing of the sidewall portion of the preform fromthe wall of the mold cavity to avoid premature chilling and reducefriction. To facilitate further the formation of the desired uniformityof sidewall thickness, the sidewall portion of the preform preferably isof slightly greater thickness adjacent the center wall portion tocompensate for the reduction in width of the wall portion due to theincline thereof which would reduce the volume thereof. To minimize thetendency for entrapment of air and to permit initial elongation o f thesidewall portion of the preform prior to ow of the plastic material ofthe preform about the plunger and into the sidewall portion, the bottomwall portion of the preform is most desirably thicker at its center. Theinitial compression thereof will produce flow from the center outwardlyto provide a time interval before material ows about the side of theplunger, thus permitting the rate of movement of the two plungersrelative to each other to be constant while effecting stretching of thematerial in the original sidewall portion of the preform.

To facilitate control over the displacement of the material from thecenter of the preform, a circumferential lip desirably cooperates withthe innermost of the plungers and extends axially therefrom toward theother plunger. The lip is of greater inner diameter than the cooperatingend of the other plunger so as to provide a radial spacing therebetweenwhen they are in operating position. In this manner, the radial spacingcontrols the material flow into the sidewall portion and thus actssimilarly to an extrusion orifice. This lip may be formed integral withthe innermost plunger or as a separate sleeve,

and the latter embodiment permits gradual retraction of the lip relativeto the plunger faces so as to avoid interference with the desired bottomcontours for the container.

The mold cavity may be provided by a plurality of split mold memberswhich are moved into abutting engagement with each or it may be a singlehollow member moved axially of the plunger means to effect clamping ofthe preform between it and the frame. The cooperating clamping surfaceof the frame may be rigid or it may be a sleeve on the frame which ismovable relative to a fixedly mounted plunger about which the preform isbeing formed. In this manner, the mold member and a movable plunger maybe movable jointly axially relative to a fixed plunger and a slidableclamping sleeve to produce the desired relative movement of the plungersand mold cavity.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a flow sheet of a processembodying the present invention for forming synthetic plastic;

FIGURE 2 is a perspective view of a plastic container produced inaccordance with the present invention;

FIGURE 3 is a sectional view of the container along the line 3 3 ofFIGURE 2;

FIGURE 4 is a fragmentary sectional view to an enlarged scale along theline 4 4 of FIGURE 3;

FIGURE 5 is a side elevational sectional view of an injection-moldedpreform used for fabricating the body portion of the containers ofFIGURES 2 4;

FIGURE 6 is diagrammatic illustration of one ernbodiment of apparatusfor conducting the present invention;

FIGURE 7 is a fragmentary side elevational section of the die andpressure-forming portion of the apparatus of FIGURE 6 at the loadingstep of the pressure-forming cycle;

FIGURE 8 is a similar sectional view after the split mold components andtop plunger have clamped the preform in position;

FIGURE 9 is a similar sectional View during the displacement of thecenter of the preform inwardly of the mold cavity;

FIGURE l0 is a similar sectional View showing in phantom line thepreform when the center portion has :been fully displaced inwardly ofthe mold cavity and showing in solid line the preform as finally moldedinto conformity with the walls of the mold assembly;

FIGURE 1l is a similar sectional view during the final cooling step ofthe cycle prior to removal of the container body from the mold assembly;

FIGURE l2 is a sectional view along the line 12-12 of FIGURE l0;

FIGURE 13 is a fragmentary sectional view to an enlarged scale of thelower plunger;

FIGURE 14 is a fragmentary sectional view diagrammatically illustratinganother embodiment of apparatus for performing the method of the presentinvention 4at the commencement of the pressure-forming cycle;

FIGURE 15 is a similar view of the embodiment Of FIGURE 14 at the end ofinward displacement of the center portion of the preform but prior tofinal deformation;

FIGURE 16 is a fragmentary sectional view diagrammatically illustratingstill 'another embodiment of apparatus for performing the presentinvention at the cornmencement `of the pressure-forming cycle;

FIGURE 17 is a similar view of the embodiment at the end of thepressure-forming cycle and showing in phantom line the displaced preformprior to nal deformation;

FIGURE 18 is a fragmentary elevational view in partial section ofanother embodiment of cooperating plungers;

FIGURE 19 is a perspective bottom view of the face of the upper plungerof FIGURE 1S;

FIGURE is a side elevational sectional View of a container having a bodyportion produced by the plungers of FIGURE 18; u

FIGURE 21 is a fragmentary bottom perspective vlew of the container ofFIGURE 20 in section to reveal internal conguration;

FIGURES 22-27 are fragmentary sectional views diagrammaticallyillustrating a further embodiment of apparatus with the apparatus atvarious progressive stages in the forming cycle;

FIGURE 28 is a fragmentary sectional view diagramgrammaticallyillustrating a still further embodiment of apparatus;

FIGURE 29 is a fragmentary partially exploded view to an enlarged scaleof the cam mechanism in the apparatus of FIGURE 28; and

FIGURE is a fragmentarily illustrated further embodiment of the preform.

DETAILED DESCRIPTION OF THE INVENTION Referring first to FIGURE l of theattached drawings, therein is a flow sheet diagrammatically illustratingthe process of the present invention as applied to a synthetic plastic,`although similar steps are employed by use of stamping or die castingor other suitable techniques to form ductile metals. Initially, apreform having a configuration predetermined to provide the desired wallsections in the finished article is prepared, preferably by injectionmolding. Next, the preform is heated uniformly throughout its entirethickness to a temperature below the molten temperature (orrecrystalliaztion temperature for metal) and at which orientation of theparticular material may be effected. This uniform temperature desirablyis effected by soaking for a sufficient period of time in air, oil orother suitable media to ensure uniformity, preferably in advance ofplacement within the mold assembly to minimize the time period requiredin processing a preform upon placement within the mold assembly.Alternatively, high-frequency heating may be employed albeit withsomewhat greater problems in ensuring control and the desired uniformityof temperature throughout.

After the preform has been heated to the desired ternperature, theperiphery of the preform is locked at one end of the mold cavity of thestretching mold assembly between a pair of cooperating plungers,although this and the preceding step may be eected together aspreviously indicated. The center portion of the preheated preform isthen displaced inwardly of the mold cavity at a substantially uniformrate while the cooperating plungers exert forging pressure upon thematerial of the center portion to effect lateral flow of some of thematerial into the side wall portion being formed by the inwarddisplacement of the center portion. Lastly, the displaced preform issubjected to internal pressure sutcient to expand or stretch it intosubstantial conformity with the configuration of the mold assemblydefined by the side walls of the mold cavity and the plunger faces.After this final displacement has been effected, the -material isallowed to set and cool, following which it is removed from the moldassembly.

Referring now to FIGURES 2-4 of the attached drawings, thereinillustrated is one embodiment of a container formed in accordance withthe present invention and having a hollow body member generallydesignated by the numeral 2 and a metal cap or cover member generallydesignated by the numeral 4. The illustrated embodiment has the Imember2 formed of plastic7 although it will be appreciated that a ductilemetal may be substituted therefor. The body member 2 is generallycylindrical and has a bottom wall portion 6 and a sidewall portion 8having a multiplicity of vertically or axially extending ribs orcorrugations 10 and an outwardly extending peripheral flange 12 at theupper end thereof. An outwardly and downwardly extending peripheral bead14 is formed at the intersection of the bottom and sidewall portions 6,8 and provides vertical spacing for the bottom wall portion from asupporting surface and a peripheral skirt cooperating with the flange12.

To enhance the peripheral rigidity (hoop strength) and resistance tovertical loading, a label or band 16 of synthetic plastic sheet materialextends about the periphery of the sidewall portion 8 and is bondedthereto by adhesive 18. In order to obtain optimum strength, the label16 desirably is uniaxially oriented in the direction peripherally of thebody element 2. In additional to providing reinforcement, the labelpermits faclie preprinting and designing of the viewable sidewall of thecontainer apart from the pressure-formed body portion. The label 16 issubstantially protected from vertical shearing forces at the upper endby the flange portion 20 of the cap member 4 which is rolled about andengages the flange 12 on the sidewall portion 8 and at the lower end bythe bead 14.

In accordance with the present invention, the sidewall portion 8 and'bottom wall portion 6 together with the intermediate bead 14 aresubstantially multiaxially oriented during the forming operation so asto possess high strength in relatively thin section. This orientation isproduced by the radial flow -or stretching of the bottom wall portion atorientation temperature and the vertical stretching of the material asit forms the elongating sidewall portion following by final peripheralor transverse stretching of the sidewall portion and further radialstretching of the bottom wall portion during final conformation of thedisplaced preform. The vertical corrugations 10 add strength in theaxial or vertical direction and the uniaxially oriented label 16 greatlyenhances the radial or peripheral strength of the body portion, thusenabling use of even thinner sections in a high-Strength composite bodymember.

Referring now to FIGURE 5, therein illustrated is an injection-moldedplastic preform generally designated by the numeral 21 and of generallydish-shaped conguration. The preform 21 has a center or bottom wallportion 22, a sidewall portion 24 and a peripheral ange portion 26extending radially outwardly at the top edge of the generally verticallyextending section 28 of the sidewall portion 24 to facilitate clampingin the mold assembly. As can be seen, the center wall portion 22 is ofgreatest thickness at the center and both surfaces converge slightlytowards the periphery in order to ensure freedom from air entrapment andboth proper and delayed ow of the plastic material between the opposedplungers, as has been explained in detail hereinbefore. Generally, adifference in thickness of about 5 to 20 percent, and preferably about10 to 13 percent, is employed. The side wall portion 24 tapers outwardlyfrom the center wall portion 22 and the surfaces thereof convergeslightly to the Wall section 28 to facilitate the forming operation andensure adequate volume of material for wall thickness due to thereduction in diameter, a difference in width of about 5 to 20 percent,and preferably about 10 to 13 percent being generally suitable dependingupon the angle of inclination. The flange 26 and immediately adjacentportion of the wall section 28 which are received within the clampingportion of the mold assembly are preferably of slightly larger dimensionthan the clamping portion so as to produce some pressure flow of thesynthetic plastic material upon clamping and thereby some orientation ofthe molecules of the material therein.

Referring now in detail to the operation of the embodiment of theapparatus and method shown in FIGURES 6 through 13, and with particularreference to the diagrammatic illustration of the major portion of theapparatus of FIGURE 6, the split mold members 30, 32 dening thegenerally cylindrical mold cavity 34 are mounted for reciprocal movementinto the operative position shown in FIGURE 6 on the upper surface ofthe bed 36 of the apparatus upon action of the clamps 38, 40 and intoinoperative position spaced from each other to permit loading andunloading. Platforms 42, 44 are joined for simultaneous, parallelmovement relative to the bed 36 by four tie rods 46 at the side marginsthereof which extend slidably through apertures 48 in the bed 36. Thelower platform 42 and thereby the upper platform 44 are mounted forreciprocal vertical movement on a precision jackscrew assembly generallydesignated by the numeral 50 and including a jackscrew 52, gear box 54,clutch and brake assembly 56 and reversible drive motor 58.

Mounted on the upper surface of the lower platform 42 is the lowerplunger assembly generally designated by the numeral 60 and having abase portion 62 and an upstanding, generally cylindrical body portion 64of lesser width than the base portion 62 so that the base portion 62provides a radially extending shoulder thereabout. 'Ihe plunger bodyportion 64 extends upwardly through a circular aperture 66 in the bed 36of larger diameter than the body portion 64 to provide radial spacingtherebetween. Through a pressure fitting 70 in the base portion 62, airor other fluid under high pressure is admitted to the main conduit 72which extends to the center of the plunger assembly and thence upwardlyinto the body portion 64. A multiplicity of outlet ducts 74, which arebest seen in FIGURE l2, extend radially therefrom and open at the sideof the body portion 64 generally in alignment with the walls of theaperture 66 in the bed 36. As seen in FIGURE 6, air is admitted to thefitting 70 through the pressure line 76 from the electrically operatedvalve 78 which releases air under high pressure from the surge tank 80wherein it is compressed by the highpressure pump 82. The surge tank 80preferably is cooled to prevent the compressed air from raising thetemperature of the synthetic plastic to the molten temperature when itcomes into Contact therewith and also to assist in cooling and settingthe preform after it has been nally expanded. To provide a tight sealupon movement into contact of the shoulder provided by the base portion62 of the lower plunger assembly 60 against the lower face of the bed36, an O-ring or other suitable sealing element 84 seats in cooperatinggrooves 86, 88 in the base portion 62 and bed 36, respectively.

The upper plunger 92 has its upper end mounted for reciprocation withinthe hydraulic cylinder 94 which is supported upon the upper platform 44and has an inner or lower face 96 which is generally planar with anarcuate recess 97 extending about the edge of its periphery. Hydraulicfluid is admitted to the cylinder 94 through the fittings 98, 100 andmoves the plunger vertically relative to the lower plunger assembly 60by action upon the piston flange 102 of the plunger 92. Shoulders orstops 104 within the cylinder 94 limit the movement toward the lowerplunger assembly 60 to prevent overcompression of the plastic sheetmaterial therebetween. To move the upper plunger 92 towards the lowerplunger assembly 60, fluid may be admitted through the valve 106 intothe upper portion of the cylinder from either the pressure control valve108 or the metering valve 110 which control the fluid fed under pressurefrom the reservoir 112 by action of the reversible pump 114 which fiuidsimultaneously is withdrawn from the lower portion of the cylinder bythe pump 114 and returned to the reservoir 112. To move the upperplunger 92 away from the lower plunger assembly 60, hydraulic fluid isadmitted to the lower portion of the cylinder from the reservoir 112 byaction of the pump 114 as fiuid is withdrawn from the upper portionthrough the valve 106 and returned to the reservoir 112.

As best seen in FIGURE 13, the upper or inner face of the lower plungerassembly 60 is provided by a face plate 116 which is generally planarwith a rounded periphery and ange which seats in a peripheral recess inthe body 64. An impulse heating element is provided by electricalresistance wires 118 woven into cloth of polytetrauoroethylene 119 orother similar heat resistant material and electrically insulated fromthe body 64 and face plate 116 by an insulating layer of glass cloth 121and an extremely thin insulating film 123 such as H-film sold by E. I.du Pont de Nemours. Current is fed to the heating element 70 throughwires (not shown) in the plunger body 64 at predetermined impulse ratesto maintain the face plate 116 of the plunger assembly 60 at theorientation temperature of the synthetic plastic material of the preform21 to prevent chilling of the preheated material. The polished steelface plate 116 may have a coating of tetrafluoroethylene or silicone toreduce friction and thereby the pressures required for ow of thesynthetic plastic material. The inner face 96 of the upper plunger 92 isprovided with a similar face plate and impulse heating element (notshown).

The split mold members 30, 32 are provided with water-cooling passages(not shown) to effect rapid chilling and setting of the plastic materialupon final conformation of the plastic material thereinto. As best seenin FIG- URES 7 and l2, the mold cavity 34 is of generally cylindricalconfiguration and has a multiplicity of axially or vertically extendingribs or corrugations 120 spaced thereabout. Adjacent the upper end, thecavity 34 is provided with a peripheral recess 122 of arcuateconfiguration extending thereabout which cooperates with the arcuaterecess 97 in the face 96 of the upper plunger 92 to provide the bead 14of the body member 2. The mold cavity 34 has a peripheral recess 124 atthe lower end thereof at the bed 36 which cooperates with the upstandingannular lip 126 on the bed 36 which extends about the aperture 66 tolock the flange 26 of the preform 21 therebetween upon closing of thesplit mold members 30, 32. The inner face of the lip 126 flaresoutwardly into the mold cavity 34.

Thus, upon closure of the mold members 30, 32, the iiange 26 is grippedwithin the recess 124 and the wall section 28 is clamped between the lip126 .and the walls of the split mold members 30, 32 which rapidly chilland set the material to minimize any tendency for this portion to bestretched. As previously stated, the flange 26 and wall section 28preferably are slightly larger than the recess 124 and the spacingbetween the mold wall and lip 126 to effect some compression and flow,thereby effecting dimensional control and some molecular orientation.

Referring now to the operation of this embodiment of apparatus, FIGURE 7shows the apparatus at the loading step in which the preform 21 whichhas been preheated uniformly throughout to orientation temperature in asoaking section (not shown) of the apparatus is inserted between thesplit mold members 30, 32 and onto the upper or inner face plate 116 ofthe lower plunger assembly 60. At this stage, the lower platform 42 andthereby the lower plunger assembly 60 have been withdraw to the lowerlimit of travel and the upper plunger 92 has been moved upwardly withinthe hydraulic cylinder 94. Current is supplied to the heating element118 under the face plate 116 of the lower plunger assembly 60 to preventpremature chilling of the preform 21.

In FIGURE 8, the clamps 33 and 40 have moved the split mold members 30,32 together and clamped the preform 21 within the recess 124 and betweenthe Wall of the cavity 34 therein and the annular lip 126. A controlcircuit (not shown) opens the valve 106 to the flow of hydraulic fluidthrough the pressure control valve 108 until the lower or inner face 96of the upper plunger 92 decends into contact with the center of thepreform 21, at which point the resistance of the plastic material todeformation produces a variation in pressure within the conduit andcloses the pressure-sensitive valve 108. Impulses are simultaneouslysent to the heating element (not shown) on the plunger face 96 toprevent cooling of the plastic material. In this initial position, thethicker center of the center wall portion 22 is firmly retained betweenthe plunger faces 96, 116.

